No, the SEO Web Vitals plugin does not send any data that you track in Matomo to any external servers. It does send the page URLs you configure to monitor the Web Vitals report data for to the Google PageSpeed API as this report requires to fetch the SEO Web Vital data from the Google PageSpeed API.

The information that is sent from your Matomo server in order for this feature to work is the following:

  1. The list of URLs you wish to monitor with the SEO Web Vitals Plugin.
    That means that you need to ensure that you are only adding publicly accessible URLs that do not contain any personal information.
  2. The authentication information required to make use of the Google PageSpeed Insights API such as the API Key required to use this API.
Previous FAQ: Requirements for SEO Web Vitals feature to work